Imaging lens, and electronic apparatus including the same

ABSTRACT

An imaging lens includes an aperture stop and first to fifth lens elements arranged from an object side to an image side in the given order. Through designs of surfaces of the lens elements and relevant optical parameters, a short system length of the imaging lens may be achieved while maintaining good optical performance.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Chinese Application No. 201510078235.7, filed on Feb. 13, 2015.

FIELD

The disclosure relates to an imaging lens and an electronic apparatus including the same.

BACKGROUND

In recent years, as portable electronic devices (e.g., mobile phones and digital cameras) become ubiquitous, much effort has been put into reducing dimensions of portable electronic devices. Moreover, as dimensions of charged coupled device (CCD) and complementary metal-oxide semiconductor (CMOS) based optical sensors are reduced, dimensions of imaging lenses for use with the optical sensors must be correspondingly reduced without significantly compromising optical performance. Imaging quality and size are two of the most important characteristics for an imaging lens.

However, in optical lens design, to reduce proportionally a size of an imaging lens is insufficient to enable such an imaging lens to be miniaturized while maintaining imaging quality. In the design process, material properties and assembly yield of such an imaging lens should also be considered.

Therefore, greater technical difficulties are encountered for a miniaturized imaging lens than for traditional imaging lenses. Producing an imaging lens that meets the requirements of consumer electronic products while having satisfactory optical performance is always a goal in the industry.

SUMMARY

An object of the disclosure is to provide an imaging lens having a shorter overall length while maintaining good optical performance.

According to one aspect of the disclosure, an imaging lens comprises an aperture stop, a first lens element, a second lens element, a third lens element, a fourth lens element and a fifth lens element arranged in order from an object side to an image side along an optical axis of the imaging lens. Each of the first lens element, the second lens element, the third lens element, the fourth lens element and the fifth lens element has an object-side surface facing toward the object side and an image-side surface facing toward the image side.

The image-side surface of the first lens element has a convex portion in a vicinity of the optical axis.

The image-side surface of the second lens element has a concave portion in a vicinity of a periphery of the second lens element.

The object-side surface of the third lens element has a concave portion in a vicinity of a periphery of the third lens element.

The fourth lens element has a negative refractive power, and the object-side surface of the fourth lens element has a convex portion in a vicinity of the optical axis.

The object-side surface of the fifth lens element has a convex portion in a vicinity of a periphery of the fifth lens element.

The imaging lens does not include any lens element with a refractive power other than the first lens element, the second lens element, the third lens element, the fourth lens element and the fifth lens element.

The imaging lens satisfies (T2+T4)/G45≦2.9, where T2 represents a thickness of the second lens element at the optical axis, T4 represents a thickness of the fourth lens element at the optical axis, and G45 represents an air gap length between the fourth lens element and the fifth lens element at the optical axis.

Another object of the disclosure is to provide an electronic apparatus having an imaging lens with five lens elements.

According to another aspect of the disclosure, an electronic apparatus includes a housing and an imaging module. The imaging module is disposed in the housing, and includes the imaging lens of the disclosure, a barrel on which the imaging lens is disposed, a holder unit on which the barrel is disposed, and an image sensor disposed at the image side of the imaging lens.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the disclosure will become apparent in the following detailed description the embodiments with reference to the accompanying drawings, of which:

FIG. 1 is a schematic diagram to illustrate surface shape and structure of a lens element;

FIG. 2 is a schematic diagram to illustrate concave and convex portions and a focal point of a lens element;

FIG. 3 is a schematic diagram to illustrate surface shape and structure of a first exemplary lens element;

FIG. 4 is a schematic diagram to illustrate surface shape and structure of a second exemplary lens element;

FIG. 5 is a schematic diagram to illustrate surface shape and structure of a third exemplary lens element;

FIG. 6 is a schematic diagram that illustrates the first embodiment of an imaging lens according to the disclosure;

FIG. 7 shows values of some optical data corresponding to the imaging lens of the first embodiment;

FIG. 8 shows values of some aspherical coefficients corresponding to the imaging lens of the first embodiment;

FIGS. 9(A) to 9(D) show different optical characteristics of the imaging lens of the first embodiment;

FIG. 10 is a schematic diagram that illustrates the second embodiment of an imaging lens according to the disclosure;

FIG. 11 shows values of some optical data corresponding to the imaging lens of the second embodiment;

FIG. 12 shows values of some aspherical coefficients corresponding to the imaging lens of the second embodiment;

FIGS. 13(A) to 13(D) show different optical characteristics of the imaging lens of the second embodiment;

FIG. 14 is a schematic diagram that illustrates the third embodiment of an imaging lens according to the disclosure;

FIG. 15 shows values of some optical data corresponding to the imaging lens of the third embodiment;

FIG. 16 shows values of some aspherical coefficients corresponding to the imaging lens of the third embodiment;

FIGS. 17(A) to 17(D) show different optical characteristics of the imaging lens of the third embodiment;

FIG. 18 is a schematic diagram that illustrates the fourth embodiment of an imaging lens according to the disclosure;

FIG. 19 shows values of some optical data corresponding to the imaging lens of the fourth embodiment;

FIG. 20 shows values of some aspherical coefficients corresponding to the imaging lens of the fourth embodiment;

FIGS. 21(A) to 21(D) show different optical characteristics of the imaging lens of the fourth embodiment;

FIG. 22 is a schematic diagram that illustrates the fifth embodiment of an imaging lens according to the disclosure;

FIG. 23 shows values of some optical data corresponding to the imaging lens of the fifth embodiment;

FIG. 24 shows values of some aspherical coefficients corresponding to the imaging lens of the fifth embodiment;

FIGS. 25(A) to 25(D) show different optical characteristics of the imaging lens of the fifth embodiment;

FIG. 26 is a schematic diagram that illustrates the sixth embodiment of an imaging lens according to the disclosure;

FIG. 27 shows values of some optical data corresponding to the imaging lens of the sixth embodiment;

FIG. 28 shows values of some aspherical coefficients corresponding to the imaging lens of the sixth embodiment;

FIGS. 29(A) to 29(D) show different optical characteristics of the imaging lens of the sixth embodiment;

FIG. 30 is a schematic diagram that illustrates the seventh embodiment of an imaging lens according to the disclosure;

FIG. 31 shows values of some optical data corresponding to the imaging lens of the seventh embodiment;

FIG. 32 shows values of some aspherical coefficients corresponding to the imaging lens of the seventh embodiment;

FIGS. 33(A) to 33(D) show different optical characteristics of the imaging lens of the seventh embodiment;

FIG. 34 is a schematic diagram that illustrates the eighth embodiment of an imaging lens according to the disclosure;

FIG. 35 shows values of some optical data corresponding to the imaging lens of the eighth embodiment;

FIG. 36 shows values of some aspherical coefficients corresponding to the imaging lens of the eighth embodiment;

FIGS. 37(A) to 37(D) show different optical characteristics of the imaging lens of the eighth embodiment;

FIG. 38 is a schematic diagram that illustrates the ninth embodiment of an imaging lens according to the disclosure;

FIG. 39 shows values of some optical data corresponding to the imaging lens of the ninth embodiment;

FIG. 40 shows values of some aspherical coefficients corresponding to the imaging lens of the ninth embodiment;

FIGS. 41(A) to 41(D) show different optical characteristics of the imaging lens of the ninth embodiment;

FIG. 42 is a schematic diagram that illustrates the tenth embodiment of an imaging lens according to the disclosure;

FIG. 43 shows values of some optical data corresponding to the imaging lens of the tenth embodiment;

FIG. 44 shows values of some aspherical coefficients corresponding to the imaging lens of the tenth embodiment;

FIGS. 45(A) to 45(D) show different optical characteristics of the imaging lens of the tenth embodiment;

FIGS. 46 and 47 are tables that list values of relationships among some lens parameters corresponding to the imaging lenses of the first to tenth embodiments;

FIG. 48 is a schematic partly sectional view to illustrate a first exemplary application of the imaging lens of the disclosure; and

FIG. 49 is a schematic partly sectional view to illustrate a second exemplary application of the imaging lens of the disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Before the disclosure is described in greater detail, it should be noted that like elements are denoted by the same reference numerals throughout the disclosure.

In the present specification, the description “a lens element having positive refractive power (or negative refractive power)” means that the paraxial refractive power of the lens element in Gaussian optics is positive (or negative). The description “An object-side (or image-side) surface of a lens element” only includes a specific region of that surface of the lens element through which imaging rays are capable of passing, namely the clear aperture of the surface. The aforementioned imaging rays can be classified into two types, chief rays (Lc) and marginal rays (Lm). Taking a lens element depicted in FIG. 1 as an example, the lens element is rotationally symmetric, where the optical axis (I) is the axis of symmetry. The region (A) of the lens element is defined as “a portion in a vicinity of the optical axis (I)”, and the region (C) of the lens element is defined as “a portion in a vicinity of a periphery of the lens element”. Besides, the lens element may also have an extending portion (E) extended radially and outwardly from the region (C), namely the portion outside of the clear aperture of the lens element. The extending portion (E) is usually used for physically assembling the lens element into an optical imaging lens system. Under normal circumstances, the imaging rays would not pass through the extending portion (E) and only pass through the clear aperture. The structures and shapes of the aforementioned extending portion (E) are only examples for technical explanation, and the structures and shapes of lens elements should not be limited to these examples. Note that the extending portions of the lens element surfaces depicted in the following embodiments are partially omitted.

The following criteria are provided for determining the shapes and the portions of lens element surfaces set forth in the present specification. These criteria mainly determine the boundaries of portions under various circumstances including the portion in the vicinity of the optical axis (I), the portion in the vicinity of the periphery of a lens element surface, and other types of lens element surfaces such as those having multiple portions.

1. FIG. 1 is a radial cross-sectional view of a lens element. Before determining boundaries of those aforesaid portions, two referential points should be defined first, central point and transition point. The central point of a surface of a lens element is a point of intersection of that surface and the optical axis (I). The transition point is a point on a surface of a lens element, where the tangent line of that point is perpendicular to the optical axis (I). Additionally, if multiple transition points appear on one single surface, then these transition points are sequentially named along the radial direction of the surface with numbers starting from the first transition point. For instance, these transition points may be the first transition point (closest one to the optical axis (I)), the second transition point, . . . and the N^(th) transition point (the farthest one from the optical axis (I) within the scope of the clear aperture of the surface). The portion of a surface of a lens element between the central point and the first transition point defined as the portion in the vicinity of the optical axis (I). The portion located radially outside of the N^(th) transition point (but still within the scope of the clear aperture) is defined as the portion in the vicinity of the periphery of the lens element. In some embodiments, there are other portions existing between the portion in the vicinity of the optical axis (I) and the portion in the vicinity of the periphery of the lens element; the number of portions depends on the number of the transition point(s). In addition, the radius of the clear aperture (or a so-called effective radius) of a surface is defined as the radial distance from the optical axis (I) to a point of intersection of the marginal ray (Lm) and the surface of the lens element.

2. Referring to FIG. 2, determining whether the shape of a portion is convex or concave depends on whether a collimated ray passing through that portion converges or diverges. That is, while applying a collimated ray to a portion to be determined in terms of shape, the collimated ray passing through that portion will be bent and the ray itself or its extension line will eventually meet the optical axis (I). The shape of that portion can be determined by whether the ray or its extension line meets (intersects) the optical axis (I) (focal point) at the object-side or image-side. For instance, if the ray itself intersects the optical axis (I) at the image side of the lens element after passing through a portion, i.e., the focal point of this ray is at the image side (see point R in FIG. 2), the portion will be determined as having a convex shape. On the contrary, if the ray diverges after passing through a portion, and the extension line of the ray intersects the optical axis (I) at the object side of the lens element, i.e., the focal point of the ray is at the object side (see point (M) in FIG. 2), that portion will be determined as having a concave shape. Therefore, referring to FIG. 2, the portion between the central point and the first transition point has a convex shape, the portion located radially outside of the first transition point has a concave shape, and the first transition point is the point where the portion having a convex shape changes to the portion having a concave shape, namely the border of two adjacent portions. Alternatively, there is another common way for a person with ordinary skill in the art to tell whether a portion in a vicinity of the optical axis has a convex or concave shape by referring to the sign of an “R” value, which is the (paraxial) radius of curvature of a lens surface. The R value is commonly used in conventional optical design software such as Zemax and CodeV. The R value usually appears in the lens data sheet in the software. For an object-side surface, positive R means that the object-side surface is convex, and negative R means that the object-side surface is concave. Conversely, for an image-side surface, positive R means that the image-side surface is concave, and negative R means that the image-side surface is convex. The result found by using this method should be consistent with that by using the other way mentioned above, which determines surface shapes by referring to whether the focal point of a collimated ray is at the object side or the image side.

3. For none transition point cases, the portion in the vicinity of the optical axis is defined as the portion between 0˜50% of the effective radius (radius of the clear aperture) of the surface, whereas the portion in the vicinity of the periphery of the lens element is defined as the portion between 50˜100% of the effective radius (the radius of the clear aperture) of the surface.

Referring to the first example depicted in FIG. 3, only one transition point, namely a first transition point, appears within the clear aperture of the image-side surface of the lens element. Portion (i) is a portion in the vicinity of the optical axis, and portion (ii) is a portion in the vicinity of the periphery of the lens element. The portion in the vicinity of the optical axis (I) is determined as having a concave surface due to the R value at the image-side surface of the lens element being positive. The shape of the portion in the vicinity of the periphery of the lens element is different from that of the radially inner adjacent portion, i.e., the shape of the portion in the vicinity of the periphery of the lens element is different from the shape of the portion in the vicinity of the optical axis (I); the portion in the vicinity of the periphery of the lens element has a convex shape.

Referring to the second example depicted in FIG. 4, a first transition point and a second transition point exist on the object-side surface (within the clear aperture) of a lens element. In the second example, portion (i) is the portion in the vicinity of the optical axis (I), and portion (iii) is the portion in the vicinity of the periphery of the lens element. The portion in the vicinity of the optical axis (I) has a convex shape because the R value at the object-side surface of the lens element is positive. The portion in the vicinity of the periphery of the lens element (portion iii) has a convex shape. Furthermore, there is another portion having a concave shape existing between the first and second transition points (portion (ii)).

Referring to a third example depicted in FIG. 5, no transition point exists on the object-side surface of the lens element. In this case, the portion between 0˜50% of the effective radius (the radius of the clear aperture) is determined as the portion in the vicinity of the optical axis (I), and the portion between 50˜100% of the effective radius is determined as the portion in the vicinity of the periphery of the lens element. The portion in the vicinity of the optical axis (I) of the object-side surface of the lens element is determined as having a convex shape due to its positive R value, and the portion in the vicinity of the periphery of the lens element is determined as having a convex shape as well.

Referring to FIG. 6, the first embodiment of an imaging lens 10 according to the disclosure includes an aperture stop 2, a first lens element 3, a second lens element 4, a third lens element 5, a fourth lens element 6, a fifth lens element 7 and an optical filter 9 arranged in the given order along an optical axis (I) from an object side to an image side. The optical filter 9 is an infrared cut filter for selectively absorbing infrared light to thereby reduce imperfection of images formed at an image plane 100. In further detail, the object side refers to the side of an object to be photographed, and the image side refers to the side of the image plane 100.

Each of the first, second, third, fourth and fifth and lens elements 3-7 and the optical filter 9 has an object-side surface 31, 41, 51, 61, 71, 91 facing toward the object side, and an image-side surface 32, 42, 52, 62, 72, 92 facing toward the image side. Light entering the imaging lens 10 travels through the aperture stop 2, the object-side and image-side surfaces 31, 32 of the first lens element 3, the object-side and image-side surfaces 41, 42 of the second lens element 4, the object-side and image-side surfaces 51, 52 of the third lens element 5, the object-side and image-side surfaces 61, 62 of the fourth lens element 6, the object-side and image-side surfaces 71, 72 of the fifth lens element 7, and the object-side and image-side surfaces 91, 92 of the optical filter 9, in the given order, to form an image on the image plane 100. Each of the object-side surfaces 31, 41, 51, 61, 71 and the image-side surfaces 32, 42, 52, 62, 72 is aspherical and has a center point coinciding with the optical axis (I).

Each of the lens elements 3-7 has a refractive power, and is made of a plastic material in this embodiment in order to be lightweight. However, at least one of the lens elements 3-7 may be made of other materials in other embodiments.

In the first embodiment, which is depicted in FIG. 6, the first lens element 3 has a positive refractive power. The object side surface 31 of the first lens element 3 is a convex surface that has a convex portion 311 in a vicinity of the optical axis (I), and a convex portion 312 in a vicinity of a periphery of the first lens element 3. The image-side surface 32 of the first lens element 3 is a convex surface that has a convex portion 321 in a vicinity of the optical axis, and a convex portion 322 in a vicinity of the periphery of the first lens element 3.

The second lens element 4 has a negative refractive power. The object-side surface 41 of the second lens element 4 is a concave surface that has a concave portion 411 in a vicinity of the optical axis (I), and a concave portion 412 in a vicinity of a periphery of the second lens element 4. The image-side surface 42 of the second lens element 4 is a concave surface that has a concave portion 421 in a vicinity of the optical axis (I), and a concave portion 422 in a vicinity of the periphery of the second lens element 4.

The third lens element 5 has a positive refractive power. The object-side surface 51 of the third lens element 5 is a concave surface that has a concave portion 511 in a vicinity of the optical axis (I), and a concave portion 512 in a vicinity of a periphery of the third lens element 5. The image-side surface 52 of the third lens element 5 is a convex surface that has a convex portion 521 in a vicinity of the optical axis (I), and a convex portion 522 in a vicinity of the periphery of the third lens element 5.

The fourth lens element 6 has a negative refractive power. The object-side surface 61 of the fourth lens element 6 has a convex portion 611 in a vicinity of the optical axis (I), and a concave portion 612 in a vicinity of a periphery of the fourth lens element 6. The image-side surface 62 of the fourth lens element 6 has a concave portion 621 in a vicinity of the optical axis (I), and a convex portion 622 in a vicinity of the periphery of the fourth lens element 6.

The fifth lens element 7 has a negative refractive power. The object-side surface 71 of the fifth lens element 7 is a convex surface that has a convex portion 711 in a vicinity of the optical axis (I), and a convex portion 712 in a vicinity of a periphery of the fifth lens element 7. The image-side surface 72 of the fifth lens element 7 has a concave portion 721 in a vicinity of the optical axis (I), and a convex portion 722 in a vicinity of the periphery of the fifth lens element 7.

In the first embodiment, the imaging lens 10 does not include any lens element with a refractive power other than the aforesaid lens elements 3-7.

Shown in FIG. 7 is a table that lists values of some optical data corresponding to the surfaces 31, 41, 51, 61, 71, 91, 32, 42, 52, 62, 72 and 92 of the first embodiment. The imaging lens 10 has an overall system effective focal length (EFL) of 3.645 mm, a half field-of-view (HFOV) of 38.068°, an F-number of 2.2, a system length (TTL) of 4.639 mm and an image height of 2.856 mm. TTL refers to a distance between the object-side surface 31 of the first lens element 3 and the image plane 100 at the optical axis (I).

In this embodiment, each of the object-side surfaces 31, 41, 51, 61, and 71 and the image-side surfaces 32, 42, 52, 62, and 72 is aspherical, and satisfies the relationship of

$\begin{matrix} {{Z(Y)} = {{\frac{Y^{2}}{R}/\left( {1 + \sqrt{1 - {\left( {1 + K} \right)\frac{Y^{2}}{R^{2}}}}} \right)} + {\sum\limits_{i = 1}^{n}\;{a_{2i} \times Y^{2i}}}}} & (1) \end{matrix}$

where:

R represents a radius of curvature of an aspherical surface;

Z represents a depth of the aspherical surface, which is defined as a perpendicular distance between an arbitrary point on the aspherical surface that is spaced apart from the optical axis (I) by a distance Y, and a tangent plane at a vertex of the aspherical surface at the optical axis (I);

Y represents a perpendicular distance between the arbitrary point on the aspherical surface and the optical axis (I);

K represents a conic constant; and

a₂₁ represents an 2i^(th) aspherical coefficient.

Shown in FIG. 8 is a table that lists values of some aspherical coefficients of the aforementioned relationship (1) corresponding to the first embodiment. Each of the columns numbered 31, 41, 51, 61, and 71 and 32, 42, 52, 62, and 72 in FIG. 8 lists the aspherical coefficients of a respective one of the object-side surfaces 31, 41, 51, 61, and 71 and the image-side surfaces 32, 42, 52, 62, and 72.

Relationships among some of the lens parameters corresponding to the first embodiment are listed in columns of FIGS. 46 and 47 corresponding to the first embodiment. Note that some terminologies are defined as follows:

T1 represents a thickness of the first lens element 3 at the optical axis (I);

T2 represents a thickness of the second lens element the optical axis (I);

T3 represents a thickness of the third lens element 5 at the optical axis (I);

T4 represents a thickness of the fourth lens element 6 at the optical axis (I);

T5 represents a thickness of the fifth lens element 7 at the optical axis (I);

G12 represents an air gap length between the first lens element 3 and the second lens element 4 at the optical axis (I);

G23 represents an air gap length between the second lens element 4 and the third lens element 5 at the optical axis (I);

G34 represents an air gap length between the third lens element 5 and the fourth lens element 6 at the optical axis (I);

G45 represents an air gap length between the fourth lens element 6 and the fifth lens element 7 at the optical axis (I);

Gaa represents a sum of the four air gap lengths among the first lens element 3, the second lens element 4, the third lens element 5, the fourth lens element 6 and the fifth lens element 7 at the optical axis (I), i.e., the sum of G12, G23, G34, and G45;

ALT represents a sum of the thicknesses of the lens elements 3-7 at the optical axis (I), i.e., the sum of T1, T2, T3, T4, and T5; and

BFL represents a distance at the optical axis (I) between the image-side surface 72 of the fifth lens element 7 and the image plane 100.

In addition, some referenced terminologies are defined herein, where:

G5F represents an air gap length between the fifth lens element 7 and the optical filter 9 at the optical axis (I);

TF represents a thickness of the optical filter 9 at the optical axis (I);

GFI represents an air gap length between the optical filter 9 and the image plane 100 at the optical axis (I);

f1 represents a focal length of the first lens element 3;

f2 represents a focal length of the second lens element 4;

f3 represents a focal length of the third lens element 5;

f4 represents a focal length of the fourth lens element 6;

f5 represents a focal length of the fifth lens element 7;

n1 represents a refractive index of the first lens element 3;

n2 represents a refractive index of the second lens element 4;

n3 represents a refractive index of the third lens element 5;

n4 represents a refractive index of the fourth lens element 6;

n5 represents a refractive index of the fifth lens element 7;

υ1 is an Abbe number of the first lens element 3;

υ2 is an Abbe number of the second lens element 4;

υ3 is an Abbe number of the third lens element 5;

υ4 is an Abbe number of the fourth lens element 6; and

υ5 is an Abbe number of the fifth lens element 7.

FIGS. 9(A) to 9(D) respectively show simulation results corresponding to longitudinal spherical aberration, sagittal astigmatism aberration, tangential astigmatism aberration, and distortion aberration of the first embodiment. In each of the simulation results, curves corresponding respectively to wavelengths of 470 nm, 555 nm, and 650 nm are shown.

It can be understood from FIG. 9(A) that, since each of the curves corresponding to longitudinal spherical aberration has a focal length at each field of view (indicated by the vertical axis) that falls within the range of ±0.03 mm, the first embodiment is able to achieve a relatively low spherical aberration at each of the wavelengths. Furthermore, since the curves at each of the wavelengths of 470 nm, 555 nm, and 650 nm are close to each other, the first embodiment has a relatively low chromatic aberration.

It can be understood from FIGS. 9(B) and 9(C) that, since each of the curves falls within the range of ±0.05 mm of focal length, the first embodiment has a relatively low optical aberration.

Moreover, as shown in FIG. 9(D), since each of the curves corresponding to distortion aberration falls within the range of ±0.5%, the first embodiment is able to meet requirements in imaging quality of most optical systems.

In view of the above, even with the system length reduced down to 4.639 mm, the imaging lens 10 of the first embodiment is still able to achieve a relatively good optical performance. Therefore, the imaging lens 10 of the first embodiment may suit a thinner product design by virtue of a shorter system length and a wider image-capturing angle while maintaining relatively good optical performance.

FIG. 10 illustrates the second embodiment of an imaging lens 10 according to the disclosure, which has a configuration similar to that of the first embodiment. The differences between the first and second embodiments of the imaging lens 10 of this disclosure reside in some of the optical data, the aspherical coefficients and the lens parameters of the lens elements 3-7. Furthermore, in the second embodiment, the object-side surface 41 of the second lens element 4 has a concave portion 411 in a vicinity of the optical axis (I) and a convex portion 413 in a vicinity of the periphery of the second lens element 2. The image-side surface 72 of the fifth lens element 7 is a concave surface that has a concave portion 721 in a vicinity of the optical axis (I) and a concave portion 723 in a vicinity of the periphery of the fifth lens element 7. In FIG. 10, the reference numerals of the concave portions and the convex portions that are the same as those of the first embodiment are omitted for the sake of clarity.

Shown in FIG. 11 is a table that lists values of some optical data corresponding to the surfaces 31, 41, 51, 61, 71, 91, 32, 42, 52, 62, 72 and 92 of the second embodiment. The imaging lens 10 has an overall system focal length of 3.622 mm, an HFOV of 37.996°, an F-number of 2.2, a system length of 4.589 mm and an image height of 2.856 mm.

Shown in FIG. 12 is a table that lists values of some aspherical coefficients of the aforementioned relationship (1) corresponding to the second embodiment.

Relationships among some of the aforementioned lens parameters corresponding to the second embodiment are listed in the columns of FIGS. 46 and 47 corresponding to the second embodiment.

FIGS. 13(A) to 13(D) respectively show simulation results corresponding to longitudinal spherical aberration, sagittal astigmatism aberration, tangential astigmatism aberration, and distortion aberration of the second embodiment. It can be understood from FIGS. 13(A) to 13(D) that the second embodiment is able to achieve a relatively good optical performance.

In comparison to the first embodiment, the second embodiment has a shorter TTL, and may have a higher yield rate since the second embodiment is relatively easier to fabricate.

FIG. 14 illustrates the third embodiment of an imaging lens 10 according to the disclosure, which has a configuration similar to that of the first embodiment. The differences between the first and third embodiments of the imaging lens 1C of this disclosure reside in some of the optical data, the aspherical coefficients and the lens parameters of the lens elements 3-7. Furthermore, in the third embodiment, the object-side surface 71 of the fifth lens element 7 has a concave portion 713 in a vicinity of the optical axis (I) and a convex portion 712 in a vicinity of the periphery of the fifth lens element 7. The image-side surface 72 of the fifth lens element 7 is a concave surface that has a concave portion 721 in a vicinity of the optical axis (I) and a concave portion 723 in a vicinity of the periphery of the fifth lens element 7. In FIG. 14, the reference numerals of the concave portions and the convex portions that are the same as those of the first embodiment are omitted for the sake of clarity.

Shown in FIG. 15 is a table that lists values of some optical data corresponding to the surfaces 31, 41, 51, 61, 71, 91, 32, 42, 52, 62, 72 and 92 of the third embodiment. The imaging lens 10 has an overall system focal length of 3.808 mm, an HFOV of 36.761°, an F-number of 2.2, a system length of 4.758 mm and an image height of 2.856 mm.

Shown in FIG. 16 is a table that lists values of some aspherical coefficients of the aforementioned relationship (1) corresponding to the third embodiment.

Relationships among some of the aforementioned lens parameters corresponding to the third embodiment are listed in the columns of FIGS. 46 and 47 corresponding to the third embodiment.

FIGS. 17(A) to 17(D) respectively show simulation results corresponding to longitudinal spherical aberration, sagittal astigmatism aberration, tangential astigmatism aberration, and distortion aberration of the third embodiment. It can be understood from FIGS. 17(A) to 17(D) that the third embodiment is able to achieve a relatively good optical performance.

In comparison to the first embodiment, the third embodiment may have a higher yield rate since the third embodiment is relatively easier to fabricate.

FIG. 18 illustrates the fourth embodiment of an imaging lens 10 according to the disclosure, which has a configuration similar to that of the first embodiment. The differences between the first and fourth embodiments of the imaging lens 10 of this disclosure reside in some of the optical data, the aspherical coefficients and the lens parameters of the lens elements 3-7. Furthermore, in the fourth embodiment. The object-side surface 71 of the fifth lens element 7 has a concave portion 713 in a vicinity of the optical axis (I) and a convex portion 712 in a vicinity of the periphery of the fifth lens element 7. The image-side surface 72 of the fifth lens element 7 has a convex portion 724 in a vicinity of the optical axis (I) and a concave portion 723 in a vicinity of the periphery of the fifth lens element 7. In FIG. 18, the reference numerals of the concave portions and the convex portions that are the same as those of the first embodiment are omitted for the sake of clarity.

Shown in FIG. 19 is a table that lists values of some optical data corresponding to the surfaces 31, 41, 51, 61, 71, 91, 32, 42, 52, 62, 72 and 92 of the fourth embodiment. The imaging lens 10 has an overall system focal length of 3.667 mm, an HFOV of 37.824°, an F-number of 2.2, a system length of 4.536 mm and an image height of 2.856 mm.

Shown in FIG. 20 is a table that lists values of some aspherical coefficients of the aforementioned relationship (1) corresponding to the fourth embodiment.

Relationships among some of the aforementioned lens parameters corresponding to the fourth embodiment are listed in the columns of FIGS. 46 and 47 corresponding to the fourth embodiment.

FIGS. 21(A) to 21(D) respectively show simulation results corresponding to longitudinal spherical aberration, sagittal astigmatism aberration, tangential astigmatism aberration, and distortion aberration of the fourth embodiment. It can be understood from FIGS. 21(A) to 21(D) that the fourth embodiment is able to achieve a relatively good optical performance.

In comparison to the first embodiment, the fourth embodiment has a shorter TTL, and may have a higher yield rate since the fourth embodiment is relatively easier to fabricate.

FIG. 22 illustrates the fifth embodiment of an imaging lens 10 according to the disclosure, which has a configuration similar to that of the first embodiment. The differences between the first and fifth embodiments of the imaging lens 10 of this disclosure reside in some of the optical data, the aspherical coefficients and the lens parameters of the lens elements 3-7. Furthermore, in the fifth embodiment, the object-side surface 71 of the fifth lens element 7 has a concave portion 713 in a vicinity of the optical axis (I) and a convex portion 712 in a vicinity of the periphery of the fifth lens element 7. In FIG. 22, the reference numerals of the concave portions and the convex portions that are the same as those of the first embodiment are omitted for the sake of clarity.

Shown in FIG. 23 is a table that lists values of some optical data corresponding to the surfaces 31, 41, 51, 61, 71, 91, 32, 42, 52, 62, 72 and 92 of the fifth embodiment. The imaging lens 10 has an overall system focal length of 3.596 mm, an HFOV of 38.436°, an F-number of 2.2, a system length of 4.478 mm and an image height of 2.856 mm.

Shown in FIG. 24 is a table that lists values of some aspherical coefficients of the aforementioned relationship (1) corresponding to the fifth embodiment.

Relationships among some of the aforementioned lens parameters corresponding to the fifth embodiment are listed in the columns of FIGS. 46 and 47 corresponding to the fifth embodiment.

FIGS. 25(A) to 25(D) respectively show simulation results corresponding to longitudinal spherical aberration, sagittal astigmatism aberration, tangential astigmatism aberration, and distortion aberration of the fifth embodiment. It can be understood from FIGS. 25(A) to 25(D) that the fifth embodiment is able to achieve a relatively good optical performance.

In comparison to the first embodiment, the fifth embodiment has a wider HFOV and a shorter TTL, and may have a higher yield rate since the fifth embodiment is relatively easier to fabricate.

FIG. 26 illustrates the sixth embodiment of an imaging lens 10 according to the disclosure, which has a configuration similar to that of the first embodiment. The differences between the first and sixth embodiments of the imaging lens 10 of this disclosure reside in some of the optical data, the aspherical coefficients and the lens parameters of the lens elements 3-7. Furthermore, in the sixth embodiment, the object-side surface 71 of the fifth lens element 7 has a concave portion 713 in a vicinity of the optical axis (I) and a convex portion 712 in a vicinity of the periphery of the fifth lens element 7. In FIG. 26, the reference numerals of the concave portions and the convex portions that are the same as those of the first embodiment are omitted for the sake of clarity.

Shown in FIG. 27 is a table that lists values of some optical data corresponding to the surfaces 31, 41, 51, 61, 71, 91, 32, 42, 52, 62, 72 and 92 of the sixth embodiment. The imaging lens 10 has an overall system focal length of 3.622 mm, an HFOV of 38.219°, an F-number of 2.2, a system length of 4.515 mm and an image height of 2.856 mm.

Shown in FIG. 28 is a table that lists values of some aspherical coefficients of the aforementioned relationship (1) corresponding to the sixth embodiment.

Relationships among some of the aforementioned lens parameters corresponding to the sixth embodiment are listed in the columns of FIGS. 46 and 47 corresponding to the sixth embodiment.

FIGS. 29(A) to 29(D) respectively show simulation results corresponding to longitudinal spherical aberration, sagittal astigmatism aberration, tangential astigmatism aberration, and distortion aberration of the sixth embodiment. It can be understood from FIGS. 29(A) to 29(D) that the sixth embodiment is able to achieve a relatively good optical performance.

In comparison to the first embodiment, the sixth embodiment has a wider HFOV and a shorter TTL, and may have a higher yield rate since the sixth embodiment is relatively easier to fabricate.

FIG. 30 illustrates the seventh embodiment of an imaging lens 10 according to the disclosure, which has a configuration similar to that of the first embodiment. The differences between the first and seventh embodiments of the imaging lens 10 of this disclosure reside in some of the optical data, the aspherical coefficients and the lens parameters of the lens elements 3-7. Furthermore, in the seventh embodiment, The object-side surface 71 of the fifth lens element 7 has a concave portion 713 in a vicinity of the optical axis (I) and a convex portion 712 in a vicinity of the periphery of the fifth lens element 7. The image-side surface 72 of the fifth lens element 7 is a concave surface that has a concave portion 721 in a vicinity of the optical axis (I) and a concave portion 723 in a vicinity of the periphery of the fifth lens element 7. In FIG. 30, the reference numerals of the concave portions and the convex portions that are the same as those of the first embodiment are omitted for the sake of clarity.

Shown in FIG. 31 is a table that lists values of some optical data corresponding to the surfaces 31, 41, 51, 61, 71, 91, 32, 42, 52, 62, 72 and 92 of the seventh embodiment. The imaging lens 1C has an overall system focal length of 3.515 mm, an HFOV of 38.904°, an F-number of 2.2, a system length of 4.576 mm and an image height of 2.856 mm.

Shown in FIG. 32 is a table that lists values of some aspherical coefficients of the aforementioned relationship (1) corresponding to the seventh embodiment.

Relationships among some of the aforementioned lens parameters corresponding to the seventh embodiment are listed in the columns of FIGS. 46 and 47 corresponding to the seventh embodiment.

FIGS. 33(A) to 33(D) respectively show simulation results corresponding to longitudinal spherical aberration, sagittal astigmatism aberration, tangential astigmatism aberration, and distortion aberration of the seventh embodiment. It can be understood from FIGS. 33(A) to 33(D) that the seventh embodiment is able to achieve a relatively good optical performance.

In comparison to the first embodiment, the seventh embodiment has a shorter TTL and a wider HFOV, and may have a higher yield rate since the seventh embodiment is relatively easier to fabricate.

FIG. 34 illustrates the eighth embodiment of an imaging lens 10 according to the disclosure, which has a configuration similar to that of the first embodiment. The differences between the first and eighth embodiments of the imaging lens 10 of this disclosure reside in some of the optical data, the aspherical coefficients and the lens parameters of the lens elements 3-7. In FIG. 34, the reference numerals of the concave portions and the convex portions that are the same as those of the first embodiment are omitted for the sake of clarity.

Shown in FIG. 35 is a table that lists values of some optical data corresponding to the surfaces 31, 41, 51, 61, 71, 91, 32, 42, 52, 62, 72 and 92 of the eighth embodiment. The imaging lens 10 has an overall system focal length of 3.486 mm, an HFOV of 39.295°, an F-number of 2.2, a system length of 4.418 mm and an image height of 2.856 mm.

Shown in FIG. 36 is a table that lists values of some aspherical coefficients of the aforementioned relationship (1) corresponding to the eighth embodiment.

Relationships among some of the aforementioned lens parameters corresponding to the eighth embodiment are listed in the columns of FIGS. 46 and 47 corresponding to the eighth embodiment.

FIGS. 37(A) to 37(D) respectively show simulation results corresponding to longitudinal spherical aberration, sagittal astigmatism aberration, tangential astigmatism aberration, and distortion aberration of the eighth embodiment. It can be understood from FIGS. 37(A) to 37(D) that the eighth embodiment is able to achieve a relatively good optical performance.

In comparison to the first embodiment, the eighth embodiment has a shorter TTL and a wider HFOV, and may have a higher yield rate since the eighth embodiment is relatively easier to fabricate.

FIG. 38 illustrates the ninth embodiment of an imaging lens 10 according to the disclosure, which has a configuration similar to that of the first embodiment. The differences between the first and ninth embodiments of the imaging lens 10 of this disclosure reside in some of the optical data, the aspherical coefficients and the lens parameters of the lens elements 3-7. Furthermore, in the ninth embodiment, the object-side surface 71 of the fifth lens element 7 has a concave portion 713 in a vicinity of the optical axis (I) and a convex portion 712 in a vicinity of the periphery of the fifth lens element 7. The image-side surface 72 of the fifth lens element 7 is a concave surface that has a concave portion 721 in a vicinity of the optical axis (I) and a concave portion 723 in a vicinity of the periphery of the fifth lens element 7. In FIG. 38, the reference numerals of the concave portions and the convex portions that are the same as those of the first embodiment are omitted for the sake of clarity.

Shown in FIG. 39 is a table that lists values of some optical data corresponding to the surfaces 31, 41, 51, 61, 71, 91, 32, 42, 52, 62, 72 and 92 of the ninth embodiment. The imaging lens 10 has an overall system focal length of 3.643 mm, an HFOV of 38.053°, an F-number of 2.2, a system length of 4.596 mm and an image height of 2.856 mm.

Shown in FIG. 40 is a table that lists values of some aspherical coefficients of the aforementioned relationship (1) corresponding to the ninth embodiment.

Relationships among some of the aforementioned lens parameters corresponding to the ninth embodiment are listed in the columns of FIGS. 46 and 47 corresponding to the ninth embodiment.

FIGS. 41(A) to 41(D) respectively show simulation results corresponding to longitudinal spherical aberration, sagittal astigmatism aberration, tangential astigmatism aberration, and distortion aberration of the ninth embodiment. It can be understood from FIGS. 41(A) to 41(D) that the ninth embodiment is able to achieve a relatively good optical performance.

In comparison to the first embodiment, the ninth embodiment has a shorter TTL, and may have a higher yield rate since the ninth embodiment is relatively easier to fabricate.

FIG. 42 illustrates the tenth embodiment of an imaging lens 10 according to the disclosure, which has a configuration similar to that of the first embodiment. The differences between the first and tenth embodiments of the imaging lens 10 of this disclosure reside in some of the optical data, the aspherical coefficients and the lens parameters of the lens elements 3-7. Furthermore, in the tenth embodiment, the object-side surface 71 of the fifth lens element 7 has a concave portion 713 in a vicinity of the optical axis (I) and a convex portion 712 in a vicinity of the periphery of the fifth lens element 7. The image-side surface 72 of the fifth lens element 7 is a concave surface that has a concave portion 721 in a vicinity of the optical axis (I) and a concave portion 723 in a vicinity of the periphery of the fifth lens element 7. In FIG. 42, the reference numerals of the concave portions and the convex portions that are the same as those of the first embodiment are omitted for the sake of clarity.

Shown in FIG. 43 is a table that lists values of some optical data corresponding to the surfaces 31, 41, 51, 61, 71, 91, 32, 42, 52, 62, 72 and 92 of the tenth embodiment. The imaging lens 10 has an overall system focal length of 3.622 mm, an HFOV of 38.216°, an F-number of 2.2, a system length of 4.594 mm and an image height of 2.856 mm.

Shown in FIG. 44 is a table that lists values of some aspherical coefficients of the aforementioned relationship (1) corresponding to the tenth embodiment.

Relationships among some of the aforementioned lens parameters corresponding to the tenth embodiment are listed in the columns of FIGS. 46 and 47 corresponding to the tenth embodiment.

FIGS. 45(A) to 45(D) respectively show simulation results corresponding to longitudinal spherical aberration, sagittal astigmatism aberration, tangential astigmatism aberration, and distortion aberration of the tenth embodiment. It can be understood from FIGS. 45(A) to 45(D) that the tenth embodiment is able to achieve a relatively good optical performance.

In comparison to the first embodiment, the tenth embodiment has a wider HFOV and a shorter TTL, and may have a higher yield rate since the tenth embodiment is relatively easier to fabricate.

Shown in FIG. 46 are tables that list the aforesaid relationships among some of the aforementioned lens parameters corresponding to the ten embodiments for comparison. When each of the lens parameters of the imaging lens 10 according to this disclosure satisfies the following optical relationships, the optical performance is still relatively good even with the reduced system length:

(1) The thicknesses of the lens elements and the air gap lengths among the lens elements may be properly reduced to shorten the system length of the imaging lens 10. However, it should be considered that the reduction may cause difficulties for assembling the imaging lens 10 and maintaining the imaging quality. Based on the aforesaid consideration, the imaging lens 10 may have better arrangement when satisfying (T2+T4)/G45≦2.9, ALT/G23≧4.2, Gaa/T4≦4.5, (T1+T3)/G23≧2.4, BFL/T3≦1.4, ALT/T1≦4.0, T3/(G12+G45)≧1.65, T1/T2≧2.6, T3/T5≧1.3, (G23+G45)/T3≦1.6, ALT/T5≧6.0 and/or (G23+G34)/T2≧2.2. In some applications, the imaging lens 10 may further satisfy 1.9≦(T2+T4)/G45≦2.9, 4.2≦ALT/G23≦5.5, 2.0≦Gaa/T4≦3.0, 2.4≦(T1+T3)/G23≦3.5, 1.0≦BFL/T3≦1.3, 3.2≦ALT/T1≦4.0, 1.65≦T3/(G12+G45)≦3.9, 2.6≦T1/T2≦3.5, 1.8≦T3/T5≦2.6, 0.7≦(G23+G45)/T3≦1.3, 6.0≦ALT/T5≦8.0 and/or 2.2≦(G23+G34)/T2≦3.4.

(2) In design of the imaging lens 10 with a shorter system length, reduction in EFL may contribute to enlargement of the field of view. Therefore, EFL tends to be small. In some embodiments, the imaging lens 10 satisfies EFL/T1≦5.7. In some embodiments, the imaging lens 10 may further satisfy 4.4≦EFL/T1≦5.7.

(3) When the surface shape of object-side surface 71 has the concave portion 713 in a vicinity of the optical axis (I) to cooperate with the convex portion 712 in a vicinity of the periphery of the fifth lens element 7, the Imaging lens 10 may have relatively better ability to correct image aberration.

Although the design of an optical system is generally associated with unpredictability, satisfaction of the aforementioned relationships may enable the imaging lens 10 to have reductions in the system length and the F-number, to have a wider field of view, to enhance imaging quality, or to have a relatively higher yield rate of assembly, thereby alleviating at least one drawback of the prior art.

To sum up, effects and advantages of the imaging lens according to the disclosure are described hereinafter.

1. The convex portion 321 that is effective to converge light cooperates with the aperture stop 2 that is disposed at the object-side surface 31, thereby enlarging the field-of-view.

2. The concave portion 422 and the concave portion 512 may contribute to correct the image aberration. In addition, design of the negative refractive power of the fourth lens element 6, the convex portion 611 and the convex portion 712 may correct the angle of light reaching the image plane 100, and the imaging quality may be ensured by such cooperation of the surface shapes.

3. In regard to each of the aforesaid ten embodiments of this disclosure, the longitudinal spherical, astigmatism and distortion aberrations are in compliance with applicable standards. The off-axis rays corresponding respectively to wavelengths of blue rays, green rays and red rays are converged around the imaging point. It is evident from the deviation range of each of the curves that deviations of the imaging points of the off-axis rays at different HFOV angles are well controlled so that the imaging lens 10 has good performance in terms of in spherical aberration, astigmatism, aberration and distortion aberration. Furthermore, since the curves with different wavelengths that respectively represent red, green, and blue rays are close to each other, the imaging lens 10 has a relatively low chromatic aberration. As a result, by virtue of the abovementioned design of the lens elements 3-7, good imaging quality may be achieved.

4. Through the aforesaid ten embodiments, it is evident that the system length of this disclosure may be reduced down to below 4.76 mm, so as to facilitate developing thinner relevant products with economic benefits.

Shown in FIG. 48 is a first exemplary application of the imaging lens 10, in which the imaging lens 10 is disposed in a housing 11 of an electronic apparatus 1 (such as a mobile phone, but not limited thereto), and forms a part of an imaging module 12 of the electronic apparatus 1.

The imaging module 12 includes a barrel 21 on which the imaging lens 10 is disposed, a holder unit 120 on which the barrel 21 is disposed, and an image sensor 130 disposed at the image plane 100 (see FIG. 6).

The holder unit 120 includes a first holder portion 121 in which the barrel 21 is disposed, and a second holder portion 122 having a portion interposed between the first holder portion 121 and the image sensor 130. The barrel 21 and the first holder portion 121 of the holder unit 120 extend along an axis (II), which coincides with the optical axis (I) of the imaging lens 10.

Shown in FIG. 49 is a second exemplary application of the imaging lens 10. The differences between the first and second exemplary applications reside in that, in the second exemplary application, the holder unit 120 is configured as a voice-coil motor (VCM), and the first holder portion 121 includes an inner section 123 in which the barrel 21 is disposed, an outer section 124 that surrounds the inner section 123, a coil 125 that is interposed between the inner and outer sections 123, 124, and a magnetic component 126 that is disposed between an outer side of the coil 125 and an inner side of the outer section 124.

The inner section 123 and the barrel 21, together with the imaging lens 10 therein, are movable with respect to the image sensor 130 along an axis (III), which coincides with the optical axis (I) of the imaging lens 10. The optical filter 9 of the imaging lens 10 is disposed at the second holder portion 122, which is disposed to abut against the outer section 124. Configuration and arrangement of other components of the electronic apparatus 1 in the second exemplary application are identical to those in the first exemplary application, and hence will not be described hereinafter for the sake of brevity.

By virtue of the imaging lens 10 of the disclosure, the electronic apparatus 1 in each of the exemplary applications may be configured to have a relatively reduced overall thickness with good optical and imaging performance, so as to reduce cost of materials, and satisfy requirements of product miniaturization.

While the disclosure has been described in connection with what are considered the exemplary embodiments, it is understood that this disclosure is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements. 

What is claimed is:
 1. An imaging lens comprising an aperture stop, a first lens element, a second lens element, a third lens element, a fourth lens element and a fifth lens element arranged in order from an object side to an image side along an optical axis of said imaging lens, each of said first lens element, said second lens element, said third lens element, said fourth lens element and said fifth lens element having an object-side surface facing toward the object side and an image-side surface facing toward the image side, wherein: said image-side surface of said first lens element has a convex portion in a vicinity of the optical axis; said image-side surface of said second lens element has a concave portion in a vicinity of a periphery of said second lens element, and said object-side surface of said second lens element has a concave portion in a vicinity of the optical axis; said object-side surface of said third lens element has a concave portion in a vicinity of a periphery of said third lens element; said fourth lens element has a negative refractive power, and said object-side surface of said fourth lens element has a convex portion in a vicinity of the optical axis; said object-side surface of said fifth lens element has a convex portion in a vicinity of a periphery of said fifth lens element; said imaging lens does not include any lens element with a refractive power other than said first lens element, said second lens element, said third lens element, said fourth lens element and said fifth lens element; and said imaging lens satisfies (T2+T4)/G45≦2.9, where T2 represents a thickness of said second lens element at the optical axis, T4 represents a thickness of said fourth lens element at the optical axis, and G45 represents an air gap length between said fourth lens element and said fifth lens element at the optical axis, said imaging lens further satisfies 2.2≦(G23+G34)/T2≦3.4, where G23 represents an air gap length between said second lens element and said third lens element at the optical axis, and G34 represents an air gap length between said third lens element and said fourth lens element at the optical axis, said imaging lens further satisfies (G23+G45)/T3≦1.6, where T3 represents a thickness of said third lens element at the optical axis.
 2. The imaging lens as claimed in claim 1, further satisfying EFL/T1≦5.7, where EFL represents a system effective focal length of said imaging lens, and T1 represents a thickness of said first lens element at the optical axis.
 3. The imaging lens as claimed in claim 2, further satisfying 4.2≦ALT/G23≦5.5, where ALT represents a sum of thicknesses of said first lens element, said second lens element, said third lens element, said fourth lens element and said fifth lens element at the optical axis.
 4. The imaging lens as claimed in claim 1, further satisfying Gaa/T4≦4.5, where Gaa represents a sum of four air gap lengths among said first lens element, said second lens element, said third lens element, said fourth lens element and said fifth lens element at the optical axis.
 5. The imaging lens as claimed in claim 4, further satisfying 2.4≦(T1+T3)/G23≦3.5, where T1 represents a thickness of said first lens element at the optical axis.
 6. The imaging lens as claimed in claim 1, further satisfying BFL/T3≦1.4, where BFL represents a distance at the optical axis between said image-side surface of said fifth lens element and an image plane.
 7. The imaging lens as claimed in claim 6, further satisfying ALT/T1≦4, where ALT represents a sum of thicknesses of said first lens element, said second lens element, said third lens element, said fourth lens element and said fifth lens element at the optical axis, and T1 represents a thickness of said first lens element at the optical axis.
 8. The imaging lens as claimed in claim 1, further satisfying 1.65≦T3/(G12+G45)≦3.9, where G12 represents an air gap length between said first lens element and said second lens element at the optical axis.
 9. The imaging lens as claimed in claim 8, further satisfying 2.6≦T1/T2≦3.5, where T1 represents a thickness of said first lens element at the optical axis.
 10. The imaging lens as claimed in claim 1, further satisfying 1.3≦T3/T5≦2.6, where T5 represents a thickness of said fifth lens element at the optical axis.
 11. The imaging lens as claimed in claim 10, wherein said object-side surface of said fifth lens element has a concave portion in a vicinity of the optical axis.
 12. The imaging lens as claimed in claim 1, further satisfying 6.0≦ALT/T5≦8.0, where ALT represents a sum of thicknesses of said first lens element, said second lens element, said third lens element, said fourth lens element and said fifth lens element at the optical axis, and T5 represents the thickness of said fifth lens element at the optical axis.
 13. An electronic apparatus comprising: a housing; and an imaging module disposed in said housing, and including an imaging lens as claimed in claim 1, a barrel on which said imaging lens is disposed, a holder unit on which said barrel is disposed, and an image sensor disposed at the image side of said imaging lens. 